Inductive proximity sensors operate based on which principle?

• A. Induction
• B. Capacitance
• C. Photoelectric
• D. Magnetic effect

Answer: (A)

Inductive proximity sensors operate on electromagnetic induction. The sensing element is a coil driven by an oscillator to create an alternating magnetic field at the tip. When a metal object enters that field, it induces eddy currents in the metal. Those eddy currents generate their own magnetic field that opposes the original field, changing the coil’s impedance. The sensor electronics detect this change and switch the output accordingly. This is why these sensors are especially suited for metal detection and remain robust in dirty or harsh environments.

Capacitance-based sensing would detect changes in capacitance due to nearby materials and dielectrics, not eddy currents. Photoelectric sensing uses light to detect objects. A purely magnetic-effect approach relies on attraction/repulsion from a magnet rather than induction of eddy currents.